chlorine in aluminium water tank

[SJFK]

I would like to ask for some assistance. We have an aluminium water tank, and late last year the water began to taste unpleasant. So we treated the water with some purifier that was chlorine based. What we did not know is that chlorine reacts badly with aluminium, corroding it and producing a slimy like jelly substance. We have, since finding this out, flushed the tank thoroughly many times, scraped the accessible part of the tank as much as possible, and filled it with boiling water. However the tank is baffled and there are large areas that we cannot get into. Is there anything we can use to help flush the crystallised chlorine and the slime out of those baffled areas? We have considered painting the inside of the tank with special interlining paint, but this is extremely expensive and again we would not be able to reach the baffled areas. We have considered replacing the tank with a stainless steel or plastic one, but this would be a last resort, as getting the tank out would be a major undertaking.
All advice would be much appreciated.

[JPA Cate]

If you're using chlorinated tap water for the cleaning, you'll be keeping the Chlorine/Aluminum reaction going.

We've a friend with an aluminum boat, and he uses two charcoal filters in his fill line to filter out the chlorine when he fills his tanks.

You're going to have to cut some cleaning ports in the tank, and use filtered water to clean it. Sorry, 'cause it's gonna be a pain.

Another potential solution is to cut off the top, cut out the baffles, make the sharp edges smooth, put a plywood floor down, install a polyethylene tank in the opening, and figure out a tie-down for it so it can't escape in a roll over.

Ann

[Cheechako]

Aluminum gets a slimy yucky white coating even without the Chlorine. Are you sure the chlorine caused your issue?

[Pete7]

Originally Posted by Cheechako

Aluminum gets a slimy yucky white coating even without the Chlorine. Are you sure the chlorine caused your issue?

Indeed, we only found out when I took the tank out due to a leak in a previous boat. Whilst washing out the tank came a white hard dog food like substance that we had been drinking from and lots of it. Didn't even bother trying to clean it, we scrapped the tank and replaced with plastic.

Pete

[UNCIVILIZED]

From a chemistry perspective, could you stop the reaction & get rid of much of the slime & chlorine precipitates by cleaning the tank with vinegar? Since chlorine is alkaline (a base) & vinegar is a mild acid. So that in theory they may cancel one another out so to speak.

I wouldn't try it on a tank without testing it first. Especially since some reactions that involve mixing 2 agents from opposite ends of the spectrum like that can be "interesting". In that there can be a lot of energy involved/created, or byproducts produced.

Also there's the chance that vinegar would be as hard on the aluminum as is the chlorine. But it may be worth looking into. As would flushing or cleaning the tanks with distilled water, whether you try the "chemistry experiment" or not.

Perhaps a grad student or professor can chime in?

[a64pilot]

I think your slime is bio based.
There are tens of thousands of boats with aluminum water tanks, if regular tap water caused a slime in the tanks and made the water taste bad, then there wouldn't be so many aluminum water tanks
I have an aluminum tank, wished I had plastic, but oh well. I have been filtering my water through a charcoal filter of a couple of years, lately when we leave the boat for a week or so initially the water has a smell, let it run for a min or two and the smell dissipates. I changed my on board filter and found a clear slime in it, I believe I have a biological growth in my lines I hope, cause if it was the tank, then it wouldn't clear up after running the water? I intend to treat just my lines with bleach

[Cheechako]

Originally Posted by a64pilot

I think your slime is bio based.
There are tens of thousands of boats with aluminum water tanks, if regular tap water caused a slime in the tanks and made the water taste bad, then there wouldn't be so many aluminum water tanks
I have an aluminum tank, wished I had plastic, but oh well. I have been filtering my water through a charcoal filter of a couple of years, lately when we leave the boat for a week or so initially the water has a smell, let it run for a min or two and the smell dissipates. I changed my on board filter and found a clear slime in it, I believe I have a biological growth in my lines I hope, cause if it was the tank, then it wouldn't clear up after running the water? I intend to treat just my lines with bleach

Nope, here's how I know: One boat had FG tanks, but heavy duty aluminum access covers. The white thick slime was only on the covers, would hang down like stalagtites (sp?) and ooze into the water.

[Island Time O25]

When I got my then 30 year old boat it came with 2 aluminum 55gal tanks. At some point I noticed a leak cause of which I traced to a few pennies lying under one of the tanks. No idea if the coins were there since the initial install or when but was a perfect example of Chemistry 101. Put a plastic tank for replacement (luckily an easy procedure in this model) and kept the other alum tank as is. Have not noticed any change in taste or texture of the water before or after or between the tanks. The alum tank which was left in place is now 35+ years old. Using the same municipal water hose at the dock since I got that boat. I did always use Brita pitcher both before and after changing one of the tanks so may be that's the ticket.

[Dulcesuenos]

Hydrogen peroxide is best for cleaning biological growth in aluminum tanks. We use a 1/4 cup per tank , fill let it sit a few hours and run the water out. If your aluminum tank has white chunks coming out it may soon need replacing. I like Triple M plastics. They custom make poly tanks for a great price.

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[jannw]

Yes, all aluminium tanks seem to get it after time ... apparently due to chlorine in the tap water ... it's ?aluminium?chloride? and manifests as slime and/or white rock-crystals ... best advice seems to be charcoal filter on the way in to remove the chlorine, mesh filter on the way out for the white crystals and a charcoal filter to remove the off smell and taste, and use hydrogen peroxide rather than chlorine if you need to treat water for bio-contamination.

Apparently it's harmless ... but doesn't taste or look so good.

I'm also in the middle of attempting to resolve this issue. Drop me a line if you happen on a good solution.

So far I've drained the tanks (thank god for wet/dry vacuums) and wire brushed by hand (which doesn't do much for the white AlCl residue, which is hard as nails). I'm next going to use mechanical abrasion (wire wheel) to try to shift the white crystals. Considering then to either leave it or to coat with food grade water tank paint (?tar?paint? or ?food?grade?epoxy).

I asked my friendly local aluminium boat builder whet they did, and they deliver the tanks raw and un-coated.

Perhaps Panope might have a good/better idea?

[Jsta_Rebel]

Originally Posted by a64pilot

I think your slime is bio based.
There are tens of thousands of boats with aluminum water tanks, if regular tap water caused a slime in the tanks and made the water taste bad, then there wouldn't be so many aluminum water tanks
I have an aluminum tank, wished I had plastic, but oh well. I have been filtering my water through a charcoal filter of a couple of years, lately when we leave the boat for a week or so initially the water has a smell, let it run for a min or two and the smell dissipates. I changed my on board filter and found a clear slime in it, I believe I have a biological growth in my lines I hope, cause if it was the tank, then it wouldn't clear up after running the water? I intend to treat just my lines with bleach

And you win the prize! Indeed the slime is bio-slime and is impervious to Chlorine. You can clean it off, but it would take a full tank of water and a very high PH cleaner to do it such as sodium hydroxide solution which would not be a good idea and tye rinse would take a lot of water, or youre going to have to figure a way to scrub out the tank. You could also look at installing a bladder inside of it. Aluminum tanks are not a good way to store fresh water. For instance, if you have a watermaker putting water into that aluminum tank, your tank is getting slowly eaten away because of the aggressive nature of the desalination RO water and adding aluminum into your water. A regular charcoal filter also will not remove it as it takes a specific "contact time" and porisity size to remove the AL ion from the water. I would NOT drink water from an aluminum tank. You can help reduce this from happening by hanging a nylon stocking filled with calcium carbonate chips inside of the tank or uses something else that will hold the calcium while allowing water to have contact with it. This gIves the agressive RO water something easier other than the aluminum to neutralize itself with. Best advice would be to replace the aluminum tank. That's what I did.

[Dulcesuenos]

According to the WHO and a few other water quality regulatory groups: Studies linking Health issues due to high aluminum content in water have proven inconclusive. Typically if it leaches out of the aluminum it appears (congeals as the white crystals) and is not just dispersed into the water.
In other words, I wouldn't rush out to replace a non leaking aluminum tank just because you are drinking RO water from it.

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[CaptTom]

What exactly is "aggressive RO water"?

I have a 36-year-old aluminum water tank. Regularly filled with tap water. Had a few crystals when I flushed it after buying the boat four years ago, no problems since.

It would be good to see some objective, evidence-based info on the pros and cons of using an aluminum tank this way.

[Dulcesuenos]

If you use dock water , w minerals, chlorinated or other, it caustic enough that over time can cause pitting etc in your tank which is also leaching of aluminum. RO or distilled water equally aggressive In its own way in that it can Leach metals from stainless, al, from aluminum and bpa's ,& pthallates (sp?) From certain plastics. (Polyethylene is OK). So pretty much whatever you put in your aluminum tank, some sort of reaction will happen over the next 20-40 years.
Again there have been Zero conclusive studies showing a link between aluminum in water and health issues.
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[a64pilot]

Originally Posted by CaptTom

What exactly is "aggressive RO water"?

I have a 36-year-old aluminum water tank. Regularly filled with tap water. Had a few crystals when I flushed it after buying the boat four years ago, no problems since.

It would be good to see some objective, evidence-based info on the pros and cons of using an aluminum tank this way.

"Real" RO water, and I do not mean to offend either Rich or Tellie, but RO water like what is used for Hemodialysis is essentially so pure that it will leach any metals it can, see water is of course the universal solvent and usually has lots of dissolved minerals etc in it, but "real" RO water is pretty much just pure water and will aggressively attack pipes etc.
I believe it is also not the best thing for you to drink.

But I believe our watermakers do not supply anything near to the level of "pure" water of a "real" RO unit, the TDS of a "real" RO unit would of course always read zero, and you do not want to drink pure water, I believe it would leech minerals from your body.

No its not poisonous but long term its not the best for you, plus it tastes like crap too.